1. Field of the Invention
The present invention relates to a printer for executing an exposure on a photosensitive material. The invention particularly relates to a printer which carries out control of exposure based on encoder pulses.
2. Description of the Related Art
In an optical printer for executing exposure by a light head, while moving a photosensitive material, pulses are generated in synchronism with the movement of the photosensitive material in order to control timing of the exposure. Then, based on these pulses, the optical printer controls the timing of the exposure. In order to generate pulses synchronous with the movement of the photosensitive material, there has been used a rotary encoder having a large number of slits on a disc, or the like. The rotary encoder is rotated in synchronism with the movement of the photosensitive material. Then, the pulses are generated corresponding to the slits in synchronism with the rotation of the rotary encoder.
However, according to this method, there has been a problem in that when a dust or the like has entered in one of the plurality of slits, it is not possible to generate a pulse corresponding to the slit in which the dust has entered. As a result, it is not possible to control the timing of exposure.
In accordance with an aspect of the present invention, a printer for executing recording onto media, comprising a head and a rotary encoder, wherein the head and the media are moved relatively.
In the relative movement between the head and the media, the media may be moved relative to the immobile head, or the head may be moved relative to the immobile media.
The rotary encoder outputs pulses corresponding to relative positions between the head and the media. The head starts recording onto the media based on the pulses output by the rotary encoder.
When the pulses from the rotary encoder have not been output within a predetermined period of time, the printer starts recording onto the media based on a lapse of the predetermined period of time.